CN100420582C - Pneumatic tire for two-wheeled vehicle - Google Patents

Abstract

A pneumatic tire for a two-wheeled vehicle, comprising: a carcass structure (2) having at least one first carcass ply (3) and at least one second carcass ply (4); a belt structure (5); a tread layer (6); a pair of sidewalls (7); wherein, each cord of the carcass ply (3, 4): determines the meridian plane of the tire (1) ( R, R'), said meridian plane passing through the intersection of said cords with the equatorial plane (XX) of the tire (1); and placed substantially perpendicular to the equatorial plane (XX) of the tire (1) and with said The meridian plane (R, R') forms a placement plane (N, N') of a placement angle (α, α') not equal to zero; and, determining said at least one first of the same meridian plane (R, R') The placement angle (α) of each cord of the carcass ply (3) and the placement angle (α′) of the corresponding cord of said at least one second carcass ply (4) are relative to said meridian plane ( R, R') have opposite signs.

Description

Pneumatic tires for motorcycles

technical field

The present invention relates to a pneumatic tire particularly suitable for equipping two-wheeled vehicles.

Background technique

It is known that tires generally comprise a carcass structure provided with at least one carcass ply, the ends of which are combined with corresponding circumferential annular reinforcing structures, which are joined to a bead core, commonly called a "bead core". An annular element in one piece; a belt structure applied at a radially outer position of the carcass structure; a pair of sidewalls applied at an axially outer position of the side surface of the carcass structure, each extending radially from one of the annular fixing structures extending radially towards said belt structure; a tread layer applied to a radially outer position of the belt structure, usually consisting of a strip of elastomeric material of suitable thickness, which is then followed by a forming operation while the tire is being vulcanized , forming longitudinal and/or transverse grooves that position the desired "tread pattern".

The carcass structure may be covered on its inner walls with an airtight layer commonly referred to as an "inner liner", consisting essentially of layers of an air-impermeable elastomeric material, adapted in tubeless tyres, to ensure the tire's own self-defense when the tire inflates. seal.

In so-called "radial" tires, each cord arranged in one or more carcass plies lies in a plane substantially radiating toward the axis of rotation of the tire, that is, it has a direction substantially perpendicular to the circumferential direction. Positioning in the direction of extension. In a different sense, in so-called "bias" tyres, the carcass structure generally comprises at least one carcass ply with cords oriented obliquely with respect to the direction of circumferential extension of the tyre; and a second carcass ply A body ply, the cords of the second carcass ply have cords extending obliquely in an orientation and crossing symmetrically with respect to the cords of the first ply.

Currently, most tires are radial due to their advantages over bias tires in terms of light weight, ride comfort, and structural strength at high speeds.

According to a recent production process, for example described in document EP928680 by the same applicant, the pneumatic tire can be formed directly on the annular support. The first carcass ply is formed by placing on said annular supports elongated sections or "belt-like elements", each said belt-like element comprising longitudinal thread-like elements combined with a layer of elastomeric material. Said strip-like elements are laid down sequentially to form the carcass structure, wherein the strip-like elements are partially superimposed on the side portions of the tyre, and are arranged circumferentially close to each other in the crown region of the tyre. Connected to the carcass ply is an annular reinforcing structure, for example comprising first and second circumferential annular inserts with an elastomeric filling interposed therebetween. The second carcass ply may be produced overlapping the first carcass ply and said annular structure. A belt structure connected to the carcass structure is then also formed in this way, which belt structure is also produced by depositing belt-like elements. Next, the tread layer and a pair of sidewalls are applied by overlapping primary blanks of elastomeric material in the form of elongated elements of appropriate dimensions, thereby forming the coils arranged in axially side-by-side and/or radially superimposed relationship. The method therefore attempts to use at least two different types of initial semi-finished products, namely: elongated elements, i.e. only segment members of elastomeric material and of substantially rectangular cross-section; strip-like elements, i.e. strips of elastomeric material, Elongated reinforcing elements, typically textile or metal cords, are incorporated therein.

Document WO 00/38906 in the name of the same Applicant describes a method of producing tires in which a carcass ply is formed by placing on an annular support a first and a second series of segments alternating with each other, said segments having The side opposite the first initial portion of the annular reinforcing structure terminating in the bead. Thereafter, a second ply is formed in the same manner as the first ply, with third and fourth series of elongated segments overlapping on opposite sides of the second initial portion of the annular reinforcing structure. The segments forming the first and second carcass plies are placed on respective deposition planes on their opposite sides with respect to the meridian plane of the annular support and have mutually intersecting side portions and radially arranged crown portions parallel offset.

Compared with tires for quadricycles, tires for two-wheeled vehicles require very specific properties involving many structural differences. The most important difference arises from the fact that when a motorcycle is traveling in a curve it must lean considerably more than its position on a straight, forming an angle (called "camber") perpendicular to the ground, usually Up to 45°, but even as wide as 65° in extreme driving conditions. Therefore, when the motorcycle faces a curve, the contact area of the tire gradually moves from the central area of the tread to the axially outermost area in the direction of the center of the bend. For this reason, motorcycle tires can be distinguished from other tires by the marked transverse curvature. This transverse curvature is usually defined by a specific ratio, which is the distance, measured on the equatorial plane of the tire, between a radially outer point of the tread and a line passing through the opposite end of the same tread side and along the The ratio of the distance measured by the tire chord between the ends. In tires for two-wheeled vehicles the value of the curvature is usually at least as high as 0.15, and the rear wheels are usually set at about 0.3 or even higher, even up to about 0.45 for the front wheels, whereas in motor vehicle tires, on the contrary, the value Usually set at about 0.05.

Currently, motorcycle tires usually have a radial carcass structure connected to a belt structure which may comprise one or more belts in the form of closed loops and essentially made of textile or metallic cords bundles, said cords being properly positioned with respect to the cords belonging to the adjacent carcass structure.

In particular, the belt structure may be made of one or more continuous cords rolled into coils arranged axially adjacent to each other and substantially parallel to the direction of circumferential extension of the tire itself (commonly referred to as "zero-degree belt layer"). In other words, the belt structure may comprise two radially superimposed layers, each consisting of an elastomeric material reinforced with cords arranged parallel to each other, said layers being so arranged that the cords of the first belt layer The threads are oriented obliquely to the equatorial plane of the tyre, while the cords of the second layer are likewise oriented obliquely, but are crossed symmetrically with the cords of the first layer (commonly known as "bias belt").

The Applicant perceives that a two-wheeled motorcycle tire with a bias belt is characterized by a high flexural rigidity in the area occupied by the tread layer, which ensures optimum behavior on bends. However, due to the relatively low edge stiffness of the sidewalls compared to the high bending stiffness of the tread layer area, vibrations may occur when running on a straight track, which can reduce the stability of the vehicle at high speeds.

In contrast, in two-wheel motorcycle tires with zero-degree belts, the bending rigidity in the tread layer region does not substantially increase, so that vibrations are controllable during operation on a straight track, especially at high speeds , and improved adhesion to the ground. However, the side rigidity may not be sufficient when the tire is running on a curve, and in addition, especially in the case of a large-sized two-wheeled vehicle, the torque transmitted from the tire to the ground may be reduced. In order to combine optimum performance both on straight lanes and on curves, motorcycle tires have been proposed in which the belt structure incorporates a pair of bias plies helically at zero degrees. Such embodiments rarely achieve a true balance of tire performance, and in any case they complicate the structure and increase weight considerably (as shown in document GB2157239).

The applicant therefore felt the need to improve the tire performance of two-wheeled motorcycles on curves, especially large-sized two-wheeled motorcycles, while maintaining comfort and stability when driving straight without adding weight.

The Applicant has found that said problem can be solved by producing a tire having a carcass structure comprising at least two plies, the cords of which lie in a plane substantially perpendicular to the equatorial plane of the tyre, and form a lay angle with the corresponding meridian plane not equal to zero, with respect to the same meridian plane, the sign of the lay angle of the cords belonging to the first carcass ply is different from the sign of the lay angle of the cords belonging to the second carcass ply . In this way, the cords of the plies of the carcass structure progressively intersect as they progress axially along the tread layer while radially along the sidewalls. Thus, the composite carcass structure is substantially of the radial ply type in the central region around the equatorial plane and of the bias ply type in the side portions of the sidewalls.

Constructing the carcass structure in this way ensures longitudinal flexibility, so that the tire provides excellent directional stability and high absorption performance of disturbing energy caused by unevenness of the ground, thus weakening the so-called "kickback" phenomenon. At the same time, the progressive intersection of the cords of the two carcass plies ensures that the resistance to slip thrust of the tire according to the invention increases progressively as the rake angle increases. This improves the stability of the tire when running on bends and the precision of driving.

The torsional stress characteristics of the tire during acceleration and braking can be obtained by improving the structure.

This quality is particularly advantageous when the belt structure comprises one or more continuous cords helical in a direction substantially parallel to the equatorial plane of the tyre, as explained in detail below. In fact, this belt structure allows the favorable combination of properties of the carcass structure to be greatly enhanced as described above, without adding weight to the overall structure of the tyre, when running on straight lanes and curves.

Contents of the invention

A first aspect of the present invention relates to a two-wheel motorcycle tire, comprising: a carcass structure having at least one first carcass ply and at least one second carcass ply, each carcass ply comprising a plurality of cords arranged substantially parallel to one another, said ply shaped into a substantially annular structure and whose ends are combined with corresponding circumferential annular reinforcing structures; a belt structure applied at a radially outer position of said carcass structure; a tread layer applied at a radially outer position of said belt structure; a pair of sidewalls applied on opposite sides of said carcass structure; characterized in that each of said carcass plies a cord: defining a meridian plane of said tire passing through the intersection of said cord with the equatorial plane of the tire; and placed substantially perpendicular to the equatorial plane of the tire and forming with said meridian plane and, determining the laying angle of each cord of the at least one first carcass ply and the laying angle of the corresponding cords of the at least one second carcass ply of the same meridian plane with opposite sign relative to the meridian plane.

In a preferred aspect, the laying twist of each cord of said at least one first carcass ply and the laying angle of the corresponding cords of said at least one second carcass ply which determine the same meridian plane are relative to said The meridian planes have opposite signs and essentially the same absolute value.

In another preferred aspect, said belt structure comprises a layer with a plurality of annular coils arranged axially side by side and wound helically at an angle of substantially zero degrees with respect to said equatorial plane of said tyre.

Description of drawings

Additional features and advantages of the present invention will become apparent from the detailed description of some preferred, but not exclusive, embodiments of the two-wheeled motorcycle tire according to the present invention. The following will be described by way of non-limiting examples with reference to the accompanying drawings, in which:

Figure 1 is a partial sectional view of a tire according to the invention;

Figure 2A is a partial side view of a portion of the carcass structure belonging to the first carcass ply as it is manufactured on a rigid annular support;

Figure 2B is a partial side view of a portion of the carcass structure belonging to the second carcass ply as it is manufactured on a rigid annular support;

Figure 2C is a partial side view showing the belt-like elements of the first carcass ply and the belt-like elements of the second carcass ply after placing them on a rigid annular support, the belt-like elements having determine the cords of the same meridian plane;

Figure 3 is a fragmentary side view of the double-ply carcass structure belonging to the tire referred to;

FIG. 4 is a horizontally developed view of a portion of the carcass structure shown in FIG. 3 .

Detailed ways

With reference to the accompanying drawings, a motorcycle tire for two-wheel vehicles is generally identified by the reference numeral 1; it comprises a carcass structure 2, preferably having first and second carcass plies 3, 4, said plies being shaped is of substantially annular construction and each ply is joined by its opposite circumferential edges with at least one annular reinforcing structure 9 to form a structure commonly referred to as a "bead".

Applied circumferentially to the carcass structure 2 in a radially outer position is a belt structure 5 on which a tread layer 6 is circumferentially superimposed; the vulcanization of the tire takes place simultaneously with the molding operation, after which On said tread layer 6 are formed longitudinal and transverse grooves, said grooves being arranged to define a desired "tread pattern".

The tire 1 also comprises a pair of sidewalls 7 applied laterally on opposite sides of said carcass structure 2 .

The carcass structure 2 may be covered on its inner wall with an airtight layer 8, generally called an "inner liner", which consists essentially of an airtight layer of elastomeric material suitable to ensure the tire's own self-defense when the tire is inflated. seal.

Preferably, the belt structure 5 comprises a layer having a plurality of annular coils arranged axially side by side and consisting of rubberized cords or strip-like elements (preferably 2 to 5) comprising some rubberized cords 5a, The cord is wound into said coil at an angle of substantially zero degrees with respect to the equatorial plane X-X of the tyre. In other words, said cords constitute a plurality of toroidal coils 5 a positioned substantially towards the rolling direction of the tyre, commonly referred to as a “zero degree” arrangement with reference to the position relative to the equatorial plane X-X of the tire 1 .

In a preferred embodiment, circumferential coils are wound on said carcass structure 2 with variable pitch to obtain a greater cord density, preferably on opposite side portions, than in the central portion of the belt structure 5 .

It should be noted here and below that even if the helix and any pitch changes make the deposition angles no longer zero degrees, these angles are so small that they can always be considered to be substantially equal to zero degrees.

Typically, the cords are textile or metal cords. Preferably, said cord is a steel cord having the property that, in a stress-strain diagram, said cord has an elongation of more than 0.4% at a load of less than 5% of the tensile strength , especially preferably in the range of 0.5-4%.

Preferably, said cords comprise high-carbon steel wires (HT), ie steel wires with a carbon content greater than 0.9%.

)扭绞在一起。If textile cords are used, said cords may consist of synthetic fibers such as nylon, rayon, PEN, PET, for example synthetic fibers preferably with high modulus, especially aramid fibers (e.g. fiber). Alternatively, composite cords may be used that include at least one low modulus thread (such as nylon or rayon) and at least one high modulus thread (such as

) are twisted together.

Optionally, the tire 1 may also comprise a layer 10 of elastomeric material arranged between said carcass structure 2 and the belt structure 5 formed by said toroidal coils 5a, said layer 10 preferably extending across The surface substantially corresponds to the extended surface of said belt structure 5 . Alternatively, said layer 10 extends on a lower surface than that of the belt structure 5, for example only on the opposite side portions thereof.

In another embodiment, an additional layer of elastomeric material (not shown in Figure 1 ) is arranged between said belt structure 5 formed by said circumferential coils 5a and said tread layer 6, Said layer preferably extends on a surface substantially corresponding to the extended surface of said belt structure 5 . Alternatively, said layer extends only along at least a part of the extension of the belt structure 5, eg on opposite side portions thereof.

纤维。In a preferred embodiment, at least one of said layer 10 and the additional layer comprises short aramid fibers dispersed in said elastomeric material, such as

fiber.

The carcass ply 2 as described above is preferably formed from two carcass half-plies 3 , 4 . Each said half-ply 3 , 4 has a plurality of cords oriented such that each cord spans the equatorial plane of the tire of the invention preferably at an angle of substantially 90°. In addition, the laying plane of each cord is substantially perpendicular to the equatorial plane X-X of said tire 1 , the laying plane is positioned relative to the meridian plane R, R' and forms with said meridian plane R, R' substantially not equal to 0 Angles α, α' (position angles) of °, said meridian plane R, R' passing through the intersection of said cord with the equatorial plane X-X.

Preferably, the carcass structure 2 is formed as described in the already mentioned document WO 00/38906. As shown in FIGS. 2A, 2B, an annular support 20 is used as a building drum, and a plurality of belt-like elements 21a, 21b are used as components of the ply, each of which has a plurality of strands parallel to each other and positioned at Cords oriented in the longitudinal dimension of the ribbon-like element itself. Each strip-like element 21a, 21b rests on said annular support 20 in a placement plane N, N' perpendicular to said equatorial plane X-X and offset parallel to the meridian plane "P", with Said meridian planes R, R' together form an angle equal to the placement angle α, α'.

According to the invention, the laying plane N of each cord of the first carcass ply 3 and the laying plane N′ of the corresponding cords of the second carcass ply 4 are offset in parallel on opposite sides with respect to the same meridian plane P .

Thus, each cord of the carcass ply straddles the equatorial plane X-X at a point belonging to the meridian plane R, R' of said tyre, the plane on which each cord is placed forms with said meridian plane the angle α, α' is not equal to 0°.

Preferably, the two plies 3 and 4 are made in such a way that the laying plane of any cord belonging to said first ply 3 forms an angle α with said meridian plane "R", with respect to said second ply The angle "α'" formed by the laying plane of the corresponding cord of 4 with the same meridian plane "R" at a radially more external position has substantially the same value, but opposite sign (Fig. 2C).

In this way, the tire 1 obtained has a two-ply carcass structure, substantially of the radial type near the equatorial plane X-X and of the substantially bias type along the sidewalls 7: in side view or in its plan development, the carcass structure is as Figures 3 and 4 previously described.

When the tire is suitable for a large-sized motorcycle, it is convenient to manufacture the carcass structure 2 having at least three carcass plies. It is desirable to make the third ply at the radially outermost position with respect to the first and second plies, and the lay angle of each cord should preferably have the same sign as the lay angle of each cord belonging to the first ply The same, especially preferably the same opening.

The fourth carcass ply can be inserted in the same way, wherein the lay angle of each cord is preferably of the same sign as the lay angle of each cord belonging to the second layer, especially preferably with the same opening.

Preferably, in the circumferential direction close to the equatorial plane of the tire 1, the strip-shaped elements are measured on the carcass ply, the strip-shaped elements have a width ranging from 5 mm to 20 mm, and a thickness ranging from 0.5 mm to 2 mm, comprising the cord The number of threads is between 4-40 and the density is preferably between 60-180 cords/dm.

The carcass ply according to the invention preferably comprises textile cords selected from those generally suitable for the manufacture of tire carcasses, for example made of nylon, rayon, PET, PEN, the strands of which The wire diameter range of the combined wire is between 0.35mm-1.5mm.

It will be appreciated that, as an alternative to the strip-like elements, a single continuous cord may be used, deposited side by side successively by placing said cords appropriately on said annular support, so as to obtain said cords having the same geometry. Carcass ply 3,4. In this case, there is no longer a plurality of cords in the strict sense, but a single cord has a plurality of segments from bead to bead and connected to each other, each of which is substantially equivalent to the Each cord of the ribbon element.

Accordingly, in this specification and in the following claims, the term "plurality of cords" refers both to an actual plurality of cords and to a plurality of cords belonging to the same cord, extending substantially from bead to bead and connected to each other. part.

Preferably, each annular reinforcing structure 9 has at least one annular insert, preferably made of metallic elongated elements arranged in substantially concentric coils, each coil optionally consisting of successive helical segments Defined by or by concentric rings formed by corresponding linear elements.

Preferably, as shown in FIG. 1 , two annular inserts 9a and 9b are provided, which when reacted axially outwardly against said ply 3 formed on said annular support 20 by means of rollers or other suitable means surface, while rolling up said thread-like elements so that at the end of the machining of the first carcass half-ply 3 , a first annular insert is made, as described in said document WO 00/38906. A charge 12 of elastomeric material is provided at an axially outer position of said first annular insert 9a. When the processing of the second ply 4 is finished, said second annular insert 9b is made in a similar manner. The deposition of a filler 13 at an axially outer position of said second annular insert 9 b completes the machining of said annular reinforcing structure 9 .

The constitutive material of the thread-like elements may be any textile or metallic material, or other material having suitable mechanical strength properties; preferably in the form of metallic cords, preferably such material is standard steel or high carbon steel.

In a preferred embodiment, the double-ply carcass structure 2 is combined with a belt structure 5 substantially solely comprising said coils 5a. In addition, the two plies 3 and 4 are preferably manufactured as described above in order to obtain substantially a tire 1 with a double-ply carcass structure of the radial type near the equatorial plane and oblique along the sidewalls 7 post type.

Claims (17)

1. A pneumatic tire for a two-wheeled vehicle, said tire having a curvature of a value at least up to 0.15, said tire comprising: A carcass structure (2) having at least one first carcass ply (3) and at least one second carcass ply (4), each carcass ply (3, 4) comprising a plurality of cords arranged in parallel, said plies (3, 4) being shaped into a substantially annular structure and whose ends engage with corresponding circumferential annular reinforcing structures (9); a radial direction applied to said carcass structure (2) a belt structure (5) at an outer position; a tread layer (6) applied at a radially outer position of said belt structure (5); a pair of side surfaces applied to said carcass structure (2) sidewalls (7) on opposite sides; It is characterized in that each cord of said carcass ply (3, 4): determining the meridian plane (R, R') of said tire (1), said meridian plane passing through the intersection of said cords with the equatorial plane (X-X) of the tire (1); and placed on a placement plane (N, N') substantially perpendicular to the equatorial plane (X-X) of the tire (1) and forming a placement angle (α, α') not equal to zero with said meridian plane (R, R') ; And, determine the laying angle (α) of each cord of said at least one first carcass ply (3) of the same meridian plane (R, R') and said at least one second carcass ply (4 ) has the opposite sign relative to the meridian plane (R, R') so that the cords of the carcass ply (3, 4) of the carcass structure They progressively intersect as they progress axially along the tread layers while radially along the sidewalls. 2. The pneumatic tire according to claim 1, characterized in that the placement angle (α ) and the laying angle (α') of the corresponding cords of said at least one second carcass ply (4) have opposite signs and substantially the same absolute value with respect to said meridian plane (R, R'). 3. A pneumatic tire as claimed in claim 1 , characterized in that each cord crosses said equatorial plane (X-X) and forms an angle with it of substantially 90°. 4. The pneumatic tire according to claim 1, characterized in that the belt structure (5) comprises a layer with a plurality of annular coils (5a) arranged axially side by side and relative to the tire Said equatorial plane (X-X) of (1) is wound helically substantially at an angle of zero degrees. 5. The pneumatic tire according to claim 4, characterized in that said coil (5a) comprises a steel cord having the property that, in a stress-strain diagram, at a load of less than 5% of the tensile strength In some cases, said cords have an elongation higher than 0.4%. 6. The pneumatic tire of claim 5, wherein the cords have an elongation ranging between 0.5% and 4%. 7. The pneumatic tire according to claim 1, characterized in that, the carcass structure (2) comprises at least three carcass plies. 8. The pneumatic tire according to claim 7, wherein the laying angle (α) of each cord belonging to the first carcass ply with respect to the meridian plane is the same as that of each cord belonging to the third carcass ply The placement angle determined by the line has a value of the same sign. 9. The pneumatic tire according to claim 8, wherein the placement angle (α) of each cord belonging to the first carcass ply is different from that of each cord belonging to the third carcass ply The openings of the laying angles of a cord are substantially the same. 10. Pneumatic tire according to claim 1, characterized in that a layer (10) of elastomeric material is provided at an interposed position between said carcass structure (2) and belt structure (5). 11. Pneumatic tire according to claim 1, characterized in that an additional layer of elastomeric material is provided at the interposed position between the belt structure (5) and the tread layer (6). 12. The pneumatic tire according to claim 10, characterized in that said layer (10) comprises short aramid fibers. 13. The pneumatic tire of claim 11, wherein the additional layer comprises short aramid fibers. 14. The pneumatic tire according to claim 1, characterized in that said carcass plies (3, 4) comprise a plurality of belt-like elements, each belt-like element comprising at least one cord. 15. The pneumatic tire according to claim 1, characterized in that, in each annular reinforcing structure (9), a first annular insert is provided at an axially outer position of the first carcass ply (3) piece (9a), and a second annular insert (9b) is arranged at an axially outer position of said second carcass ply (4). 16. Pneumatic tire according to claim 15, characterized in that each annular reinforcing structure (9) comprises a filling (12) of elastomeric material in a position axially external to said first annular insert (9a) ). 17. A pneumatic tire according to claim 16, characterized in that each annular reinforcing structure (9) comprises a filling ( 13).

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